/**
 * Created with IntelliJ IDEA.
 * Description:
 * User: GodK
 * Date: 2024-03-28
 * Time: 12:18
 */

// 2、无头双向链表实现
public class MyLinkedList {
    static class ListNode {
        public int val;
        public ListNode prev;//前驱
        public ListNode next;//后继

        public ListNode(int val) {
            this.val = val;
        }
    }

    public ListNode head;
    public ListNode last;

    //头插法
    public void addFirst(int data) {
        ListNode node = new ListNode(data);
        if(head == null){
            head = last = node;
        } else {
            head.prev = node;
            node.next = head;
            head = node;
        }
    }


    //尾插法
    public void addLast(int data) {
        ListNode node = new ListNode(data);
        if(head == null){
            head = last = node;
        } else {
            last.next = node;
            node.prev = last;
            last = node;
        }
    }


    //任意位置插入,第一个数据节点为0号下标
    public boolean addIndex(int index, int data) {
        try {
            checkIndex(index);
        }catch (IndexNotLegalException e) {
            e.printStackTrace();
        }
        if(index == 0){
            addFirst(data);
            return true;
        }
        if(index == size()){
            addLast(data);
            return true;
        }
        ListNode node = new ListNode(data);
        ListNode cur = findIndex(index);
        node.prev = cur.prev;
        cur.prev.next = node;
        node.next = cur;
        cur.prev = node;
        return true;
    }

    private void checkIndex(int index) {
        if(index < 0 || index > size()) {
            throw new IndexNotLegalException("双向链表插入index位置不合法: "+index);
        }
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key) {
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key){
                return true;
            }
            cur = head.next;
        }
        return false;
    }

    private ListNode findIndex(int index) {
        ListNode cur = head;
        while(index != 0){
            cur = head.next;
            index--;
        }
        return cur;
    }

    //删除第一次出现关键字为key的节点
    public void remove(int key) {
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key){
                if(cur == head){
                    head = head.next;
                    if(head != null){
                        head.prev = null;
                    } else {
                        last = null;
                    }
                } else {
                    cur.prev.next = cur.next;
                    if(cur == last){
                        last = last.prev;
                    } else {
                        cur.next.prev = cur.prev;
                    }
                }
                return;
            }
            cur = cur.next;
        }
    }


    //删除所有值为key的节点
    public void removeAllKey(int key) {
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key){
                if(cur == head){
                    head = head.next;
                    if(head != null){
                        head.prev = null;
                    } else {
                        last = null;
                    }
                } else {
                    cur.prev.next = cur.next;
                    if(cur == last){
                        last = last.prev;
                    } else {
                        cur.next.prev = cur.prev;
                    }
                }
            }
            cur = cur.next;
        }
    }


    //得到单链表的长度
    public int size() {
        int count = 0;
        ListNode cur = head;
        while (cur != null) {
            cur = cur.next;
            count++;
        }
        return count;
    }

    public void display() {
        ListNode cur = head;
        while(cur != null){
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }

    public void clear() {
        ListNode cur = head;
        while (cur != null){
            ListNode curN = cur.next;
            cur.prev = null;
            cur.next = null;
            cur = curN;
        }
        head = last =null;
    }
}
